Use of Exfoliative Specimens and Fine-Needle Aspiration Smears for Mutation Testing in Lung Adenocarcinoma

Abstract

Objective: Cytology specimens are considered to be a promising alternative for detecting driver mutations in lung cancer patients. We aimed to explore the suitability and utility of various cytology samples of non-small-cell lung cancer (NSCLC) patients for mutation testing. In addition to mutation detection, the importance of preanalytic factors was discussed. Design: A total of 116 cytology samples including 32 controls comprising pleural effusions, bronchial washings, and direct fine-needle aspiration (FNA) smears were included in the study for the detection of EGFR, KRAS, and Her-2/neu gene mutations. Tumor content was checked by microscopic evaluation. Tumor enrichment was done by scraping direct smears. DNA yield was assessed before selecting the method of mutation detection. Sanger sequencing and real-time PCR-based methods were used. Results: Overall, 20.23% EGFR mutations and 2.74% KRAS mutations were observed in this study. Nondriver genetic polymorphisms were observed in EGFR exon 20 in 37% cases. The coexistence of the EGFR mutation and EGFR polymorphism was seen in 7 cases. DNA yield was better in pleural effusions and bronchial washings. Real-time PCR was used in specimens of low DNA yield. Conclusions: Cytology samples are useful in ascertaining molecular diagnostic information for treatment purposes if they are optimized judiciously in their preanalytic phase.